Herbicide Persistence and Rotation to Cover Crops

1 Herbicide Persistence and Rotation to Cover Crops Research conducted by Bill Curran and Dwight Lingenfelter Extension Weed Science, Penn State University Presented by 1-800-767-9441. Home of the Tillage Radish Introduction The question about whether corn or soybean Herbicide programs herbicides with shorter half-lives (the time it takes for 50% of the will pose a problem for establishing fall Cover Crops has become a active ingredient to dissipate) are always less of a concern. common question, particularly in areas of severe drought where corn is harvested earlier than normal and the desire to plant a Of course several factors influence the rate of dissipation such Cover /forage crop is strong.

2 If you look at the Rotation crop as rainfall, soil texture and soil pH, etc., however, most guidelines restrictions for corn and soybean herbicides in the Penn State generally are for normal conditions ( not severe drought). In Agronomy Guide (click here to view) (Tables and ), general, products with a 4 month or less Rotation restriction for the you will see that many products limit Rotation to alfalfa and/or the species of interest, close relative, or sensitive species ( clovers). clovers as well as some of the small grains. should pose little problem. These products typically have half-lives of less than 30 days.

3 Species sensitivity can play a role if only a small This is a good place to start when thinking about Rotation to fall amount of residue is necessary to cause injury and the Herbicide Cover Crops . However, these tables are inadequate because these persists. Quite often, small seeded legumes and grasses like the cash crop Rotation restrictions may be due to the concern for clovers and ryegrass and mustard species like canola are very Herbicide residues accumulating in forage or feed rather than sensitive to some herbicides . carryover injury. If the crop is not going to be harvested and consumed by livestock or humans, then the primary concern The following table provides some Persistence and carryover is carryover injury and achieving an acceptable stand that information for some commonly used corn and soybean provides the benefits of a fall or winter Cover .

4 Cover Crops that are herbicides . not harvested can be planted after any Herbicide program, but the grower assumes the risk of crop failure. Some of this information is our best guess and only pertains to the eastern US, not heavy Midwest soils or the western US where soils have high soil pH and Two factors become important when trying to predict the rainfall is lower. potential for carryover injury to rotational Crops . 1. How long the Herbicide lasts or persists in the soil, assuming that it has soil activity. 2. How sensitive the rotational crop is to potential Herbicide residues.

5 Research conducted and used with permission by Bill Curran and Dwight Lingenfelter Extension Weed Science, Penn State University 10/15/2012. Corn Common corn herbicides , estimated half-lives, cash crop restrictions and potential to injure fall Cover Crops . Normal Half Life Cash Crop Fall Cover Crops Herbicide Active Ingredient Rate/acre (days)1 Restrictions OK to Plant Concern for Other Wait 30 days before Amine formulations more Plant anything 30 days after 2,4-D 4S 2,4-D 1-2 pt 7. application All grasses planting sensitive water soluble and can broadleaves leach into seed zone nicosulfuron/.

6 Accent 75DF/ oz/ Sensitive Crops have 10-18 Fall cereal grains, Small seeded legumes, More persistent in high nicosulfuron 21. Steadfast 75DF oz month restriction ryegrass mustards, sorghum pH soils (> 7). + rimsulfuron Can plant corn, sorghum, and More persistent in high pH. Cereals, ryegrass, Atrazine 4L atrazine 1-2 qt 60 soybean the following year Sorghum species legumes and mustards soils (> 7). Rates < 1 lb/acre (some products) can allow more flexibility Small seeded legumes and 15 of total precipitatio required Cereals, ryegrass, from application to planting Balance Pro 4L isoxaflutole 2 fl.

7 Oz 50-120 vegetables have a 10 to 18 Fall cereal grains legumes and mustards Rotation Crops except soybean, month restriction barley, wheat, sorghum, sunflower Callisto Sequential applications 10 to 18 months for legumes Small seeded legumes, (includes Lumax, Lexar, mesotrione 3-6 lf. oz 5-32 and vegetables All grasses (PRE fb POST) increase the mustards potential for injury Halex GT). Clarity/Banvel 4S Only at high rates or Anything can be planted dicamba 16-24 fl. oz 5-14 15 days per 8 fl. oz/acre for All Crops less than 120 days after 120 days with (Distinct and Status) small grains after application 24 fl.

8 Oz/acre or less Annual ryegrass or Higher rates and later Dual II Mag metolachlor pt 15-50. Labeled for use on many Almost anything other small seeded applications more of a Crops grasses potential problem Four months for wheat, 15 of total precipitation tembotrione Small seeded legumes, required from application Capreno + thiencarbazone 3 fl. oz 50-120 10 months for barley, Wheat, triticale, rye mustards, sorghum to planting Rotation Crops sorghum, oats and alfalfa except wheat isoxaflutole Four mo. for wheat, 9 mo. for 15-30 of total precipitation Corvus Wheat, triticale, rye Small seeded legumes, fl.

9 Oz 50-120 barley and 17 mo. For alfalfa, from application to planting + thiencarbazone oats, sorghum, and canola mustards, sorghum for sensitive Crops Harness 7E Four mo. for wheat and 9 mo. Food or feed residues Nonfood/feed winter acetochlor 2 pt 10-20 Most Crops should (Degree, Warrant) for alfalfa and clovers rather than crop injury Cover Crops are allowed be fine may be a concern after corn harvest Alfalfa, canola, soybean Wheat, barley, oats, Although many broad- rye are allowed after leaves are restricted, We have not seed this Impact topromesone fl. oz 14 and sunflower have a 9 mo.

10 3 mo. Ryegrass should Impact does not have Herbicide carryover in PA. restriction also be OK much soil activity Four mo. for cereal grains, Unknown - small seeded Other Crops may be seeded Laudis tembotrione 3 fl. oz 14 10 mo. for sorghum, canola, Cereal grains after legumes, mustards after a successful field and alfalfa 4 mo. could be a problem bioassay Cash crop restrictions ranged Cereal grains and Peak 57WG prosulfuron 1 oz 9-152 from 10 mo. for soybean and sorghum are labeled, Small seeded legumes, More persistent in high (& Spirit) tobacco to 22 mo. for alfalfa other grasses mustards pH soils (> 7).